Process of drawing refractory metal



UNITED STATES PATENT OFFICE.

JUNZO HISAMOTO, OF NAGOYA CITY, JAPAN, ASSIGNOR TO TOYO-KAGAKU-YAKIN-KA-BUSIKI-KAISHA (THE ORIENTAL CHEMICAL METALLURGIC COMPANY, LIMITED),

OF TOKYO, JAPAN.

PROCESS OF DRAWING REFRACTORY METAL.

No Drawing.

To all whom it may concern:

Be it known that I, JUNzo HIsAMo'ro, a subject of the Emperor of Ja an,residing at 22 Miyademachi, Nagoya ity, Aichiken, Japan, have inventedcertain new and useful Improvements in Processes of Drawing RefractoryMetal, of which the following is a specification.

This invention relates to a method of drawing wire made of refractorymetals which are liable to become contaminated with carbon while beingdrawn or during annealing of the same, and has for its object theprevention of such contamination and the production of uniformfilamentary wires suitable as illuminants for electrical incandescentlamps.

tion, I insert them in a tube or cylinder of metal having about the samehardness as the slugs. This tube may be a metal such as malleable nickelor an alloy of nickel and chromium or may be of steel although I do notconfine myself to such metals for even silver will be found serviceablein some cases. The tube may be somewhat larger than the slug ofrefractory metal so that I may pack therein a small quantity of somemetallic oxid powder such as thoria or magnesia, or ceria, or zirconiaor other substance capable of being drawn down and annealed withoutclogging the tube or cylinder. The material selected for the filling ofthe tube should be in fine powder and must be tightly packed with theslug in the tube and any air or moisture may be pumped or drawn out or arupture of the metal of the tube might be caused during the later stagesof the draw-' ing down of the wire.

The cylinder, when properly packed, is then treated as though made ofsolid metal in the manner of drawing tungsten wire and can be readilyreduced to filamentary size.

When drawn to the desired diameter the,

Specification of Letters Patent.

Patented July 6, 1920.

Application flied April 24, 1919. Serial No. 292,405.

compound wire may then be cut into lengths suitable for incandescentlamps and the inner metal drawn out of the inclosing tube, or the tubemay be dissolved in acid or other solvents and thus leavethe wire clear.Another way of removing the tube metal from the refractory wire is tocut it in lengths suitable for lamp filaments, place them in a flashingjar, connecting them with electrical terminals and after exhausting theturning on a proper current on the tube and contents snfficient to meltthe tube from the contained wire but not enough heat to injure the wire.

In using this invention it may be proper in some cases to insert therefractory slug in a cylinder or tube without using the oxid filling andthis is particularly so where it is found better to remove the tubemetal by means of acids or other solvents or by meltin" the tube fromthe wire.

It will be proper to so regulate the diameter of the tube to thediameter of the slug so that the tube will be strong enough to allow ofits being drawn down the entire distance with the slug and yet have itthin at the finishing dies.

In the method hereinbefore described the refractory slugs are set forthas being hammered and worked before placing in the tube or cylinder butthey may instead be placed in t e tube before being worked and then behammered or forged after being'inserted in the tube.

In place of using one tube I may in some cases use a double tube, forinstance, a tube of some ductile metal such as, for example, copper,silver or nickel, may receive the slug of refractory metal and this tubebe placed in an outer tube the tubes then being drawn or rolled in thesame manner as already herein set forth. A steel tube is preferably em)loyed as the outer cylinder.

After the drawing operation the outer tube is removed by dissolving itin hydrochloric acid or sulfuric acid. There then remains on the drawnWire a thin coating or shell of the material of the inner tube. Lastlythe thin coating can be removed by melting it or by dissolving it inacid. The refractory oxid may be packed in the inner tube ashereinbefeore described.

This invention is characterized by that a refractory metal which is poorin its malleability and inserted in the metal tube made of a malleablemetal is subjected to an elongation by means of operating said metaltube, so that whenever the metal tube is operated to an appropriatesize. the metal wire inserted therein can be made very fine compared tothe size of the tube; according to this process. there is no necessityto employ the accurate and expensive diamond dies in the case when diesare required to operate such metal wire as the inexpensive copper dieswhich have larger holes are sufiicient to accomplish the purpose;furthermore, according to this improved process, the metallic oxidationcaused by a high temperature of metal when it is drawn through die holesis utterly avoided, and a metallic filament in any small size can easilybe obtained by adjusting the diameter of the outer tube to be employed,so that the incandescent filaments are economically produced by thisprocess, and the outer tube dissolved in this method is utilized to makesome salts as a by-product of this process, thereby not causing any lossin an economy.

What I claim is;

1. The method of drawing refractory metal to a filamentary diameterwhich consists in surrounding a refractory slug of metal with arefractory oxid, placing these evenly in a metal tube, drawing the tubeand contents to a filamentary size and removing the tube and oxid fromthe inclosed refractory metal.

2. The method of drawing refractory metal to a filamentary diameterwhich consists in surrounding a refractory slug of tungsten with arefractory oxid, placing these in a metal tube, exhausting theairtherefrom, hammering and working the tube and contents at a heatedtemperature, drawing it to a filamentary size and removing the tubemetal and oxid from the inclosed tungsten.

In testimony whereof I have aflixed my signature in the presence of twowitnesses.

J UNZO HISAMOTO.

lVitnesses lucnom RoJIMA, TAFUIIOHI NAKAYAMA.

